In a large mixing bowl, combine the flours and water and stir to combine as best as possible (the mixture will be “shaggy”). Cover with plastic wrap and set in a warm location for 45 minutes.
400 grams bread flour, 200 grams whole wheat flour, 460 grams filtered water
After 45 minutes (this gives the mixture time to autolyse), add the starter and salt to the flour/water mixture and stir well.
90 grams ripe sourdough starter, 12 grams salt
Cover with plastic wrap and set aside for 4 to 6 hours (see next step for steps to strengthen dough during the 6 hours).
We will perform a set of folds to strengthen the dough during the first two hours of this “bulk fermentation” time.
Every 30 minutes, uncover the bowl of dough. Dip your hands into warm water (this keeps the dough from sticking to your hands). Slide your hands down around the top of the dough. Lift this side of the dough up and fold it down over the side opposite. Turn the bowl 90 degrees and repeat lifting and folding until you have lifted and folded each of the four sides of the dough. Replace the plastic wrap and leave the dough to set for another 30 minutes.
Repeat twice more.
After you’ve completed three sets of lifting and folding the dough, do a final set of dough-strengthening folds. Slide your dampened hands around the dough sides (right and left). Lift the dough straight up from the bowl. The ends will dangle down and stretch. Do not let the dough break. Set the dough straight back down on itself. Rotate the bowl 90 degrees and repeat, completing four lift and stretch sets.
Now let the dough sit for about four more hours undisturbed to complete bulk fermentation.
At this time, the dough should be smooth and rounded, holding its shape with somewhat of a dome toward the edges of the bowl. Large bubbles may appear under the surface of the bread.
Now it’s time to shape the bread into a loaf. We will shape one round loaf but you can divide the dough at this point and make two smaller loaves or shape them into ovals, baguettes, or whatever you desire.
Place the liner in the banneton and sprinkle with rice flour (the rice flour doesn’t have gluten so it won’t stick to the bread dough).
Lift the dough from the bowl and place it into the basket, flipping it upside down so that the smooth “top” of the dough is now face down in the basket. Tuck the excess dough onto itself to form a neat upside-down loaf.
Sprinkle rice flour on top of the dough to prevent it from sticking to the plastic wrap and also to dust the baking dish when it flips over into the pan at baking time.
Wrap the entire basket with plastic wrap so that it is sealed up. Place in the refrigerator overnight or for at least 12 hours.
When it’s time to bake, place the Dutch oven into the oven and preheat to 500°F. Allow the oven and Dutch oven to heat at this temperature for at least 30 minutes, but preferably 1 hour.
Remove the dough from the refrigerator and discard the plastic wrap.
Carefully remove the hot Dutch oven from the oven. Then quickly flip the banneton basket upside down to dump the dough into the center of the Dutch oven.
Score the loaf with the lame. This gives the bread an area for steam to escape and the loaf to puff during baking.
Quickly place the lid on the Dutch oven and return it to the oven. Bake for 20 minutes at 500°F.
Reduce the oven temperature to 450°F and carefully remove the lid - turning the lid away from you so that the steam doesn’t rise out toward you.
Continue baking for about 10 minutes longer or until the crust is deep golden brown.
Remove from the oven and transfer the loaf to a cooling rack to cool completely.